Netherlands Patent Application No. 7807027 discloses a matrix circuit of the above-mentioned type in which in the difference producing circuit a level correction signal coming from the output of the relevant level detection circuit is subtracted from the relevant colour difference signal, the third colour difference signal being subtracted therefrom before it is applied to the input of the level detection circuit. The third colour difference signal is obtained from the difference between the first and the second colour difference signals, respectively, and the relevant level correcting signal, which causes two intercoupled control loops.
The invention has for its object to avoid this coupling of control loops.